Stoping Macro if Connection is Lost - sql

Question

I have a series of codes that run when designated, the first is a connection check. If it is successful then it allows the code to continue, if not it stops it altogether. I am worried however about what happens when the connection is lost after this process. There is data on a local table that is uploaded to our SQL server during this process, if the connection terminates mid download it looks like sometimes the data is still transferred but not if it happens right away.
The second part of the code, deletes all the local tables contents which contain employee information, then downloads the new data so if there were any updates the most recent information is provided.
I am trying to figure out if there is a method or code that can be implemented to tell the query to stop running as soon as connection is lost, or if there is a way to undo it if it happens.
Or would it be a good idea to combine the connection code with the upload and delete codes so it runs every time before it initiates a process?
The connection code that runs at the beginning is:
Public Function StartUp()
Dim cnn As ADODB.Connection
Dim localrst As New ADODB.Recordset
Dim remoterst As New ADODB.Recordset
On Error Resume Next
Set cnn = New ADODB.Connection
cnn.Open "Provider=PRO; Data Source=SOURCE; Initial Catalog=CAT;" _
& "User Id=ID; Password=PW;"
If cnn.State = adStateOpen Then
MsgBox ("You have an established connection with the L&TD SQL Server Database and the CDData table has been uploaded to the server.")
Else
MsgBox ("Cannot connect to SQL Server. Data will be stored locally to CDData Table until application is opened again with an established connection.")
End
End If
On Error GoTo 0
' MsgBox ("Please wait while the database is updating, this may take a moment.")
End Function
As you can see, I placed an END before the END IF so if there is no connection it just ends altogether.
The UPLOAD code is
Public Function Update()
Dim cdb As DAO.Database, qdf As DAO.QueryDef
Dim rs As DAO.Recordset
Dim err As DAO.Error
' Const DestinationTableName = "AC_CDData"
Const ConnectionString = _
"ODBC;" & _
"Driver={SQL Server Native Client 10.0};" & _
"Server=SERV;" & _
"Database=DB;" & _
"UID=ID;" & _
"PWD=PWD;"
Set cdb = CurrentDb
Set qdf = cdb.CreateQueryDef("")
Set rs = CurrentDb.OpenRecordset("CDData", dbOpenTable)
qdf.Connect = ConnectionString
Do While Not rs.EOF
qdf.SQL = "INSERT INTO AC_CDData_1(EmployeeID, EmployeeName, Region, District, Function1, Gender, EEOC, Division, Center, MeetingReadinessLevel, ManagerReadinessLevel, EmployeeFeedback, DevelopmentForEmployee1, DevelopmentForEmployee2, DevelopmentForEmployee3, DevelopmentForEmployee4, DevelopmentForEmployee5, Justification, Notes, Changed, JobGroupCode, JobDesc, JobGroup) " & _
"Values (" & _
"'" & rs!EmployeeID & "', " & _
"'" & rs!EmployeeName & "', " & _
"'" & rs!Region & "', " & _
"'" & rs!District & "', " & _
"'" & rs!Function1 & "', " & _
"'" & rs!Gender & "', " & _
"'" & rs!EEOC & "', " & _
"'" & rs!Division & "', " & _
"'" & rs!Center & "', " & _
"'" & rs!ManagerReadinessLevel & "', " & _
"'" & rs!MeetingReadinessLevel & "', " & _
"'" & rs!EmployeeFeedback & "', " & _
"'" & rs!DevelopmentForEmployee1 & "', " & _
"'" & rs!DevelopmentForEmployee2 & "', " & _
"'" & rs!DevelopmentForEmployee3 & "', " & _
"'" & rs!DevelopmentForEmployee4 & "', " & _
"'" & rs!DevelopmentForEmployee5 & "', " & _
"'" & rs!Justification & "', " & _
"'" & rs!Notes & "', " & _
"'" & rs!Changed & "', " & _
"'" & rs!JobGroupCode & "', " & _
"'" & rs!JobDesc & "', " & _
"'" & rs!JobGroup & "')"
qdf.ReturnsRecords = False
On Error GoTo Update_qdfError
qdf.Execute dbFailOnError
On Error GoTo 0
rs.MoveNext
Loop
rs.Close
Set qdf = Nothing
Set cdb = Nothing
Set rs = Nothing
Exit Function
Update_qdfError:
For Each err In DAO.Errors
MsgBox err.Description, vbCritical, "Error " & err.Number
Next
End Function
So is there a way I can modify the Connection code and add it to the update code (minus the message boxes) so if the connection cuts off it will terminate the code?

Answer 1

Did you try out transactions? Wrapping your insert script inside a transaction will not change the database until you've explicitly committed the transaction. If the data connection is lost during the inserts, the commit will never be called, and the SQL Server data won't be changed.
See http://msdn.microsoft.com/en-us/library/office/ff196400%28v=office.15%29.aspx